Elastic fluid generator



March 2, 194 3. CALDWELL T AL 2,312,876 I ELASTIC FLUID GENERATOR Filed Jan. 23, 1942 Ihven tors: Andrew Caldwell,

VoPras A.Ellhott, I? '-IAW y Their Attorney.

Patented Mar. 2, 1943 STATES Application January 23, 1942; Serial No.- 427,960

6 Claims.

The present invention relates to elastic fluid generators in which an operating medium is heated in a plurality of tubes and discharged therefrom into a drum or liquid vapor separating vessel. More specifically the inventionrelates to supporting arrangements for boiler tubes which are suspended as catenaries. The invention is of particular importance in connection with mercury boilers operated at high-temperatures.

The object of our invention is to provide an improved construction and arrangement of tube supports whereby stresses in the tubes and the elements connected thereto are reduced to a minimum.

For a consideration of what we believe to be novel and our invention, attention is directed to the following description and the claims appended thereto in connection with the accompanying drawing.

In the drawing Fig. 1 illustrates a mercury boiler partly in section in accordance with our invention; and Fig. 2 is an enlarged detail view of a part of Fig. 1.

The mercury boiler illustrated in the drawing has lower walls l9 forming a combustion chamber II and upper walls !2 forming a convection chamber for receiving combustion gases discharged from the chamber II. The walls it of the combustion chamber are lined with a plu-' rality of substantially vertically arranged heating tubes I i. Upper portions of at least some of the heating tubes M are arranged in groups or bundles [5 which are twisted and extended across the lower portions of the convection space with their ends connected to the side wallof a vessel or mercury liquid separating device Iii. The vessel or drum IS in the present arrangement is located outside the right-hand Wall of the convection space.

The groups or bundles of tubes or tube portions l5 form slag screens to reduce the discharge of slag from the combustion chamber into the convection chamber and a stack connected to the latter. Banks of mercury heating tubes H are located in the lower portion of the convection space and have discharged ends [8 connected to the top of th drum l6. Ordinarily the inlets of the tubes I! are connected to the outlets of some of the heating tubes in the combustion chamber H. A steam superheater I9 is disposed in an upper portion of the convection chamber 13 to utilize available heat energy from the gases discharged from the lower portion of the combustion chamber. A mercury boiler of this type is more fully disclosed in the patent to B. P. Coulson, Jr. 2,202,835, issued June 4, 1940, and assigned to the same assignee as the present application.

The boiler is supported on a foundation 2%] and a plurality of spaced pillars or beamsof structural iron 2|, 22. The drum I6 is held on the pillars 22 by means includinghorizontal beams 23.

An important feature of our invention is the arrangement for supporting the groups of tubes I5 which, as stated above, are suspended as catenaries. The right hand ends of the tubes are fused to openings i n the side wall of the drur'n l5. Thus the drum is and its supporting means 22, 2'3 constitute a 'substantially rigid support for the discharge ends of the tubes l5. The lefthand portions of the tubes l5 are flexibly or yieldingly held on a supporting arrangement 24. This supporting arrangement includes a wall portion 25 (Fig. 2) made of heat insulating mate'- rial 26 covered on its outside by a metal cover or enclosure 21. The wall portion 25 is movably independent on the other portions of the wall l2 and suitably sealed thereto to reduce the discharge of gases from the convection chamber through clearances 28 formed between the Wall portion 25 and the other portions of the walls I2. The wall portion 25 is attached to a structure including vertical beams 29 and horizontal beams 38 rigidly secured together by means of slanted structural ironsti. Thus the wall portion 21 with the beams and irons 29,39. 3| form a rigid structure. This structure is vertically supported by means of a plurality of links}! having lower ends pivotally connected to the beam 30 and upper ends pivotally held on cars 33 of horizontal beams or rigid supporting elemerits 34. The wall}? is biased horizontally outward by means including compression springs 3 5 held between extensions of the cover 2'! and adjacent portions of the stationary walls l2 In addition the wall 26* is biased outward, that is, away from the convection chamber by another compression spring means 35 which has ends suitably linked to the vertical beam ,29 and to a supporting structure 31 held on the beams 2!.

The left-hand end portions of the groups of tubes I5 are held on links which latter are pivotally'supported on,irons 3'9 fastened to the beams 29 and- 30. Each tube or groupsof tubes forms a catenary and as such exerts horizon'tal and'vertical forces ori its supports. Each portion of the tubes themselves is subjected to such forces. The left-hand parts of the tubes are substantially straight and inclined towards the nanzontal by an angle alpha. It is desirable to maintain this angle alpha substantially constant because for a certain anglealpha a-ininimum turning moment is exertedby the tubes on the drum or, from another viewpoint, in order to maintain at aniinimuin the turning moment exerted by intermediate portions, of the tubes on their end portions fused to the drum. The angle alpha is a measure of the sag of the tube, that is, the vertical distance between their upper ends connected to the drum located at a higher level and their lower portions connected to the flexible support described above and located at a lower level. In accordance with our invention the tubes are connected to a support which biases the tubes horizontally with a force responsive to changes in sag, which increases with rising temperature, causing expansion of the tubes. This is accomplished by the flexible supporting means including the springs 35 and 36 described above. The horizontal force F exerted on a support by a catenary structure is equal to F=WO /8A in which W is the weight per foot of the structure, is the span of the catenary and A is the sag. Thus, this horizontal force is inversely proportional to the sag. An increase in temperature during operation of the boiler causes an increase in sag of the tubes and accordingly a decrease of the horizontal force F. As this force F is equal to or balanced by the force of the springs 35, 36 such springs force the catenary tubes outward, that is, towards the left in the drawing as the sag increases. This outward movement during operation continues until the supporting force exerted by the springs balances the horizontal force exerted by the tubes, resulting in the maintenance of a substantially constant catenary shape with changes of temperature and consequently in a constant turning moment exerted on. the discharge portions of the tubes.

Similarly, a decrease in temperature causing contraction of the tubes and a reduced sag effects an increase in the horizontal force F of the tubes. This increased force F is balanced by increased compression of the springs 35 and 36 whereby the wall portion 25 is moved inward, that is, towards the convection chamber until the two forces balance and the tubes l assume their original catenary shape.

Thus, with our invention we have accomplished an improved construction and arrangement for supporting boiler heating tubes arranged to form catenaries and subject to varying temperatures during operation. In a preferred embodiment of our invention, asdescribed above, one end of each tube is rigidly connected to a (rigid support and another end portion of each tube is connected to a yieldable support. The latter is biased horizontally by means forcing the tube or tubes outward, that is, away from the heating chamber, with a force varying in response to changes of the tube temperature or the sag of the tube. The horizontal biasing means in the example described above is in the form of a plurality of springs connecting a movable wall portion of the boiler for holding the tubes to a rigid support.

Having described the method of operation of our invention, together with the apparatus which wenow consider to represent the best embodiment thereof, we desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A boiler comprising a wall forming a heating chamber, a heating tube in the chamber forming a catenary, a support secured to the wall for rigidly supporting one end of the tube,

and means for supporting the other end of the tube, said means including a horizontally movable member to maintain the sag of the tube substantially constant.

2. A boiler comprising a wall forming a heating chamber, a tube for heating operating medium extending across the chamber and having the shape of a catenary, means rigidly supporting one end of the tube, and means yieldingly supporting another portion of the tube and exerting a horizontal force thereon varying in response to changes in sag of the tube in order to maintain the sag of the tube substantially constant.

3. A boiler comprising a wall forming a heat ing chamber, a tube having a catenary shape in the chamber for receiving operating medium to be heated, a rigid support connected to one end of the tube, and means including a spring for supporting the other end of the tube to maintain the catenary shape of the tube substantially constant with changes in temperature.

4. A boiler comprising a wall forming a heating chamber, a liquid vapor separating drum, a plurality of heating tubes having portions lining the wall of the chamber and other portions with a catenary shape extending across the chamber and having discharge ends rigidly secured to the drum, and a supporting structure for the catenary shaped tube portions, said structure including means for exerting a horizontal force on the tubes varying in response to changes in temperature of the tubes to maintain the catenary shape of the other portions substantially constant.

5. A boiler comprising a wall forming aheating chamber, a drum, a plurality of tubes having portions lining the wall in the chamber and other portions shaped as catenaries and extending across the chamber to form slag screens, the other portions having discharge ends rigidly connected to the drum, and a supporting structure for said other tube portions to prevent changes of their catenary shape upon changes of temperature, said supporting structure including-a wall portion of the boiler connected to said other tube portions and means biasing the wall portion horizontally with a force varying in response to changes in sag of the other tube portions. I

6. A boiler comprising a wall forming a heating chamber, a drum, a plurality of tubes having portions lining the wall in the chamber and other portions shaped as catenaries and extending across the chamber to form slag screens, the other portions having discharge ends rigidly connected to the drum, and a supporting structure for the other tube portions to prevent changes of their catenary shape upon changes of temperature of the tubes, said supporting structure comprising a wall portion horizontally movable independent of the remaining wall of the boiler and linked to the other tube portions, beams secured to and reinforcing said wall portion, means including links vertically supporting the beams and permitting horizontal movement thereof, and means including a spring connected to the beams and biasing the wall portion horizontally against the horizontal force created by the catenary shape of the other tube portions.

ANDREW CALDWELL. VORRAS A. ELLIOTT. 

